This section is intended to introduce various aspects of the art that may be topically associated with embodiments of the present techniques. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
As conventional hydrocarbon reservoirs (e.g., high-permeability onshore reservoirs, high-permeability reservoirs located in shallow ocean water, etc.), are depleted other hydrocarbon sources must be developed to keep up with energy demands. Such reservoirs may include any number of unconventional hydrocarbon reservoirs, such as heavy oil reservoirs, deep-water oil reservoirs, and natural gas reservoirs.
One such unconventional hydrocarbon resource is natural gas produced from formations that form unconventional gas reservoirs, including, for example, shale reservoirs and coal seams. Because unconventional gas reservoirs may have insufficient permeability to allow significant fluid flow to a wellbore, many of such unconventional gas reservoirs are currently not considered as economically attractive sources of natural gas. However, natural gas has been produced for years from low permeability reservoirs having natural fractures. Furthermore, a significant increase in shale gas production has resulted from hydraulic fracturing, which can be used to create extensive artificial fractures around wellbores. When combined with horizontal drilling, which is becoming more commonly used in industry, the hydraulic fracturing may allow formerly unattractive reservoirs to become commercially viable.
Currently, many shale gas, tight gas, and tight oil formations are hydraulically fractured using a combination of water, proppant, and chemicals to create higher connectivity in the formation and enhance both recovery rates and cumulative volumes produced from a single horizontal wellbore. This method has proven to be economically viable, but has encountered some opposition. Some of the concerns involve the release of chemicals into the subsurface, the large quantities of water utilized in the process, and the noise and truck traffic associated with the process.
The industry is also concerned with several aspects of hydraulic fracturing, including the volumes of water, and the costs. The volumes of water used in hydraulic fracturing are often very large, and may exceed several million barrels of water per fracture job. In many locations in the United States, water is quite scarce, so water sourcing can be an issue. In addition, a substantial fraction of the injected water, for example, between 10-50%, can be produced back and may require treatment. Transport, treatment, and disposal of this water can be quite costly, for example, in excess of $10/bbl in parts of the northeastern United States. Moreover, a typical hydraulic fracturing process can require 10 or more stages with each stage costing $100,000-$300,000.
As a result of some of these issues, some governmental entities are proposing bans on hydraulic fracturing, jeopardizing the access to the resources. Technologies that can provide access to shale gas resources without the use of hydraulic fracturing may become the preferred means of production enhancement in these formations by many government bodies.
Several patents and pieces of literature discuss creating lateral wells to increase production from reservoirs without fracturing. For example, U.S. Pat. No. 5,533,573 to Jordan et al. (the '573 patent) discusses a method for completing multi-lateral wells and maintaining selective re-entry into laterals. A first lateral well is drilled from a primary well bore and a string of external casing packers and a packer bore receptacle are run into the first lateral well. Once the orientation of the packer bore receptacle is determined, an orientation anchor of a retrievable whipstock assembly is mounted thereto. Thereafter, a second lateral well may be drilled. Once the second lateral well is drilled, the whipstock assembly may be retrieved and replaced with a scoophead diverter assembly which also includes an orientation anchor for mating with the packer bore receptacle. At this time, a string of external casing packers may be run into the second lateral well through the scoophead diverter assembly. Finally, a selective reentry tool is run into the scoophead assembly. The selective re-entry tool includes a diversion flapper for selecting either the first or second lateral well bore. Selective re-entry is desirable for the purpose of performing well intervention techniques. The re-entry tool may be actuated by a device located on a coil tubing work string which may be operated from the surface.
U.S. Patent Application Publication No. 2011/0017445, by Freyer, discloses a method and device for making lateral openings out of a wellbore in a well formation. In a disclosed method, fluid is flowed through a motherbore tubular, such as a completion or production pipe, and then through a needle pipe that is aimed at the formation. The needle pipe, which includes at least one pipe section, is positioned inside or outside a motherbore tubular and the pipe sections is positioned to be telescopically displaceable with regard to another pipe.
An important factor in drilling a lateral well off of a main wellbore is the penetration of a casing. For example, wells may have a concrete casing, an iron casing, a steel casing, and the like. A number of developments have focused on drilling lateral wells from a cased well, including, for example, the '573 patent, which details a more traditional lateral drilling procedure.
U.S. Pat. No. 6,920,945 to Belew et al. (the '945 patent) describes a method and system for facilitating horizontal drilling in a well. A shoe that has a passageway extending from an upper opening to a side opening is positioned in the well. A rod connected to a casing mill end through a universal joint is inserted into the well casing and through the passageway in the shoe until the casing mill end abuts the well casing. The rod and casing mill end are then rotated until the casing mill end forms a perforation in the well casing. The rod and casing mill end are then withdrawn from the well casing, and a nozzle attached to the end of a flexible hose is extended through the passageway to the perforation. Fluid is then ejected from the nozzle and impinges and erodes subterranean formation material.
U.S. Patent Application Publication No. 2010/0187012, by Belew et al., (the '012 application) describes a method and apparatus for laterally drilling through a subterranean formation. An exemplary apparatus includes an internally rotating nozzle for facilitating drilling through a subterranean formation. The internally rotating nozzle is mounted internally within a housing connected to a hose for receiving high pressure fluid. The rotor includes at least two tangential jets oriented off of center for ejecting fluid to generate torque and rotate the rotor and cut a substantially cylindrical tunnel in the subterranean formation.
However, neither the '945 patent nor the '012 application indicates that the apparatus at the end of the flexible hose either drills through the casing prior to drilling into the formation or is capable of doing so. Instead, as described in the '945 patent, a separate tool that includes a casing mill is used to cut holes in the casing. This tool is then withdrawn prior to insertion of the apparatus that is used to drill into the formation.
These references disclose the formation of laterals drilled from a central wellbore. However, none of the reference discussed above disclose drilling small lateral wells from a main wellbore in a single operation that penetrates a well casing and a subterranean formation.